Wikipedia:Reference desk/Archives/Science/2010 September 20

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September 20

Update to Aug 22, 2010 question by me re "Instructions for Filtering Water in Urdu Language"

This post was a notification that a question had been resolved. Moved to the original archived thread SpinningSpark 07:54, 20 September 2010 (UTC)

Uses of natural rubber

Dear friends, I'd like to know that which type of natural rubber use for tires and tubes?

amin —Preceding unsigned comment added by 80.191.71.237 (talk) 07:53, 20 September 2010 (UTC)

The Pará rubber tree (Hevea brasiliensis), is the cheapest and primary source of natural rubber and so it would be this one. --Aspro (talk) 08:02, 20 September 2010 (UTC)

However, the average car tyre contains only 14% natural rubber and 27% Synthetic rubber[1]; apparently it takes 26 litres of oil to make each one[2]. Alansplodge (talk) 19:00, 20 September 2010 (UTC)

The amount of organic compound X found in 26 barrels of oil is not at all like using 26 barrels of oil. Good way of getting me shocked though. I mean, if each tire really consumed 26 barrels of crude, I'd be surprised tires wouldn't be expensive-r. John Riemann Soong (talk) 00:21, 21 September 2010 (UTC)

Er, check your units, John...that's 26 liters – about an eighth of a barrel – per tire, not 26 barrels. TenOfAllTrades(talk) 00:46, 21 September 2010 (UTC)

About 5 Imperial gallons in old money. Alansplodge (talk) 12:44, 22 September 2010 (UTC)

What is the proper English name of this lamp?

whatsitsname

What is the name of this lamp? I've tried to check around Gas-discharge lamp and List of light sources, but didn't see something quite like that. It may be a diode after all, but it's main function is (obviously) generating light.

The piece on the picture was built in Hungary in the 70's (by Tungsram) and have completely disappeared from the market after the regime shift of '89. (And just hung up the sales guy at GE Lighting who said that the probability of it ever manufactured again is zero since all the misc parts [glass, metal parts] will be discontinued due to new EU regulations over tungsten lamps. Sad.) I have been told that similar items (figure lamps) are still on sale in Russia, Bulgaria and such but since I am not able to figure out the name I cannot really search for it. The dictionary suggested "glow lamp" which seems not to be the particular phrase to convey the meaning... :-( Ideas, or maybe for-sale items (in private email)? Thank you. --grin ✎ 08:41, 20 September 2010 (UTC)

Novelty neon lamp, similar to the flame flicker bulbs. Other designs are still obtainable. tritek taiwan corporation --Aspro (talk) 09:08, 20 September 2010 (UTC)

I Agree with Aspro. To quote wikihow: "Flicker Flame" light bulb is a form of specialty lighting which produces a candle-like "flame" effect. The bulbs use two metal plates in an evacuated bulb, filled with the rare-earth gas neon, to create a dancing orange glow. Although these bulbs are appreciated by many lighting enthusiasts, they can be difficult to find. EverGreg (talk) 13:37, 20 September 2010 (UTC)

“Rare-earth gas”? Odysseus1479 (talk) 00:54, 21 September 2010 (UTC)

I think they mean noble gas, also erroneously known as "rare gas". ~AH1^(TCU) 01:02, 21 September 2010 (UTC)

Thanks, fellow wikipedians. :-) I worry that if I write this you stop providing new informations, but a feedback seems necessary. I wouldn't have guessed it's a "neon", too. --grin ✎ 11:04, 21 September 2010 (UTC)

I'm pretty sure it was made after 1981, the first appearance of the cartoon character (Vuk) depicted on it. --131.188.3.20 (talk) 19:25, 24 September 2010 (UTC)

Transmembrane protein

Why do you we find alpha helix str. in transmembrane region of membrane protein? —Preceding unsigned comment added by 123.252.174.26 (talk) 09:40, 20 September 2010 (UTC)

The alpha helix structure is stable within phospholipid membranes, so transmembrane proteins can remain transmembrane proteins (and not fall out of the membrane). Our article on transmembrane domains provides some more information. Cheers, Mattopaedia ^{Say G'Day!} 10:43, 20 September 2010 (UTC)

absorbers

can i know names of absorbers that can absorb carbon mono oxide —Preceding unsigned comment added by Harikishanchem (talk • contribs) 09:43, 20 September 2010 (UTC)

Do you mean absorbers that actually remove the carbon monoxide from the air so it won't poison anybody? --Chemicalinterest (talk) 10:57, 20 September 2010 (UTC)

Hopcalite is used in rescue equipment where carbon monoxide is a risk. Wikipedia -as always- has an article on it. It is a convesion into CO2 however. --Aspro (talk) 11:16, 20 September 2010 (UTC)

By absorber...you mean a scrubber or air purifier right?Smallman12q (talk) 11:53, 20 September 2010 (UTC)

The hopcalite is a catalyst that makes carbon monoxide react with oxygen to make carbon dioxide. Normally this happens very slowly, unless the CO is ignited. --Chemicalinterest (talk) 15:13, 20 September 2010 (UTC)

As Chemicalinterest intimates: the only other way deal with CO that is practical -- is to burn it off. This term is used to mean catalytic burning. It is used on nuclear submarines etc. It does not absorb but converts the Co to CO2. Have we answered your question???--Aspro (talk) 19:52, 20 September 2010 (UTC)

And if you are interested in temporary absorption of carbon monoxide, haemoglobin has this property, this is due to transition metals forming a carbonyl complex like nickel carbonyl. Other molecules do this too like oxygen or the toxic phosphorus trifluoride or the exotic fluoroborylene aka boron monofluoride which has no article yet. Graeme Bartlett (talk) 22:33, 20 September 2010 (UTC)

Do all Lewis acids that bind CO catalyse its reaction to CO2? Take piano stool complexes for example. Do the solvents have to be oxygen-free? John Riemann Soong (talk) 00:17, 21 September 2010 (UTC)

Keep in mind though, too much carbon dioxide can also lead to poisoning through hypercapnia. ~AH1^(TCU) 01:00, 21 September 2010 (UTC)

Massive dose of radiation

What can be seen immediately after someone receives a massive dose of radiation? --Chemicalinterest (talk) 14:53, 20 September 2010 (UTC)

A large puff of smoke! Can you be a little more precise.--Aspro (talk) 15:04, 20 September 2010 (UTC)

Our article on radiation poisoning has a reference table of the symptoms of various levels of radiation exposure. For whole-body exposure of 30 gray or higher, it lists nausea, vomiting, diarrhea, headache, fever, seizures, tremor and ataxia, followed by death. Gandalf61 (talk) 15:10, 20 September 2010 (UTC)

(edit conflict)Smoke??? A radiation dose of 50 grays, for example. Could someone tell just by looking at the person that they have just received the dose of radiation? (No infrared radiation is present.) --Chemicalinterest (talk) 15:11, 20 September 2010 (UTC)

The article states what happens after half an hour or so. What can be seen immediately, if anything can be seen? --Chemicalinterest (talk) 15:11, 20 September 2010 (UTC)

Radiation burns develop pretty quickly, depending on the type of radiation. Physchim62 (talk) 15:46, 20 September 2010 (UTC)

(ec) At most a radiation burn if the source was intense and close. --Mr.98 (talk) 15:47, 20 September 2010 (UTC)

Radiation_poisoning#Exposure_levels lists that for massive doses, vomiting begins immediately so that would be the first symptom/visual sign? Exxolon (talk) 15:53, 20 September 2010 (UTC)

The article says that nausea and vomiting occur immediately with high levels of exposure. The extent of visible radiation burns, if any, will depend on the type of radiation - beta radiation is heavily absorbed by the skin and causes visible burns; gamma radiation and X-rays are absorbed throughout the body and may not cause immediately visible burns. Anyone with 50 grays of whole-body exposure is not going to be walking around for more than a few minutes. Gandalf61 (talk) 15:57, 20 September 2010 (UTC)

Chemicalinterest has used a superlative which one would think mean more than the word 'high' by an order of a magnitude or more. A pidgin which finds itself in a 9 MW radar wave guide would show immediate symptoms of being in the wrong place at the wrong time. This is not a question that can be properly answered yet. What about the effect of being in the focus of some of the Gigawatt lasers? They test aircraft component by exposing them to the direct radiation of nuclear device which vitrifies the surrounding rock of the test chamber. This is all radiation.--Aspro (talk) 18:33, 20 September 2010 (UTC)

Radiation generally means ionizing radiation. See dictionary definition (1. particles emitted by radioactive substances: energy emitted in the form of particles by substances such as uranium and plutonium, whose atoms are not stable and are spontaneously decaying. This energy can be converted into electric power, but it can also cause severe or fatal health problems to people who are exposed to it. Microsoft Encarta Dictionary). It can mean general electromagnetic radiation, but it is normally called just that. --Chemicalinterest (talk) 19:58, 20 September 2010 (UTC)

No. Its ionizing radiation that normally means ionizing radiation. Don't put things back to front just because you did not phrase your question properly.--Aspro (talk) 20:52, 20 September 2010 (UTC)

Oh, come on, I think we all knew with a 95% confidence rate that he meant ionizing radiation. Comet Tuttle (talk) 21:29, 20 September 2010 (UTC)

That's what I was trying to say. The primary definition of radiation in my dictionary is ionizing radiation. The second one is (2. physics energy emitted in rays or waves: energy emitted from a source in the form of rays or waves, e.g. heat, light, or sound Microsoft Encarta). Please do not exhibit the Cuddlyable3 syndrome. --Chemicalinterest (talk) 21:34, 20 September 2010 (UTC)

No. Radiation means energy that radiates. It is where the noun 'radio' comes from. Madam Curie became familiar with the term and used it. Don't put the latter expansion of use before the former. Primary does not mean secondary just because it suits you.--Aspro (talk) 21:52, 20 September 2010 (UTC)

You knew perfectly well what he meant, unless you are robotically tone-deaf to context. Comet Tuttle (talk) 22:21, 20 September 2010 (UTC)

The meaning of the term radiation in the context of a phrase like "massive dose of radiation" is not ambiguous, to this native english speaker at least. Vespine (talk) 22:45, 20 September 2010 (UTC)

Roger that, Vespine. I'm sure 99% of people would take it for granted that ionising radiation was the kind intended. Especially when Chemicalinterest mentioned a dosage in grays. Chemicalinterest might like to know that one person, Cecil Kelley, involved in a criticality accident was quoted as saying "I'm burning up!". Within ten minutes of the exposure he had erythema and was almost unconscious. If you have access to external websites, this Los Alamos Science-published piece has much more information on the incident. If not, get in touch and I'll paraphrase it for you. Brammers (talk/c) 23:09, 20 September 2010 (UTC)

I don't mean to derail this discussion, but for anyone with an interest in radiation, criticality accident is really a great article, as well as Demon core and the people involved in those incidents.. It's hard to describe how I felt the first time I read about those incidents, just an incredible mix of horror and wonder in equal measure. Vespine (talk) 00:20, 21 September 2010 (UTC)

Aspects of scientific studies

One illustration in a reading I'm doing for school is a story of scientists studying cognitive energy in a group of students based on food: they make students memorise numbers of different sizes and allow them to choose between two different types of dessert afterward. The scientists observe that the students who must memorise larger numbers tend to choose chocolate cake, while the students who have smaller numbers tend to choose fruit salad; from this, the scientists conclude that memorising larger numbers takes up enough brain resources that students have a hard time choosing the healthier dessert. Now for my question — do studies such as this take into account the subjects' likes and dislikes for certain types of food? If I were one of these individuals, regardless of how large of a number I would have to memorise, I'd go for the fruit because I don't like chocolate, and I suppose that there are individuals who will go for chocolate because they think they're too skinny and need to gain weight. Two final things — I'm a library science student, not a psychology student; this isn't at all a request for help with homework. Secondly, the story is on pages 9 and 10 of this document. Nyttend (talk) 15:44, 20 September 2010 (UTC)

Done properly, this sort of research would take that into account. I don't have time to read the paper you linked, but the normal way of doing this sort of thing is to make sure that your test groups are large enough that these sorts of personal preferences average out. Additionally, the groups might not be split up randomly. Sometimes they intentionally split them up evenly. (ie: They might have done a survey ahead of time, found that they had eight people who professed a strong love for healthy deserts, and made sure that four of them wound up in each group.)APL (talk) 15:51, 20 September 2010 (UTC)

The article Randomized controlled trial is a bit heavy, but it discusses the subject better than I just did. The article mostly talks about medical trials, but they don't have to be medical. I this case the 'intervention' isn't some experimental drug, it's just being forced to memorize large numbers. APL (talk) 15:56, 20 September 2010 (UTC)

And it's probably healthy to be a little dubious of the kind of conclusion made. To me it seems to be a big jump between "we noticed a small but statistically significant correlation between choosing the cake and memorizing the larger numbers" to "well this must have to do with 'brain resources' and metabolization of energy." I mean one can come up with all sorts of alternative interpretations even if one accepts their data is good and the experiment itself was done well. (Chocolate, for example, is not exactly a pharmacologically neutral substance. We might be learning more about the cognitive effects of chocolate here than the amount of energy needed for memorization.) --Mr.98 (talk) 15:57, 20 September 2010 (UTC)

(edit conflict)Psychology#Controlled experiments has :"A true experiment with random allocation of subjects to conditions allows researchers to infer causal relationships between different aspects of behavior and the environment." (Causal seems a bit strong, but okay because ideally it does allow that). Presumably, the students were randomly assigned into the two groups such that it could be statistically safe to say that there was no a priori difference between one group's average food preference and the other's. If the experiment was done right, in other words, the only difference between the two groups before they were offered a choice was that one group memorized a 7-digit number and the other a 2-digit number, in which case, yes, it accounted for that. (I'm surprised that there was enough difference in "cognitive effort" between these two tasks to account for such a measurable result -- it sounds like it may have been poorly designed, I wonder if any other studies have replicated support it. See also The Magical Number Seven, Plus or Minus Two for a sense of the "cognitive effort" involved here.) WikiDao ☯ (talk) 16:05, 20 September 2010 (UTC)

People who have had to work hard feel sorry for themselves and decide that they "deserve" to eat chocolate. It's well known that people treat food as a reward and a comfort. That's just one alternative explanation for the effect. Itsmejudith (talk) 16:31, 20 September 2010 (UTC)

(Note) In case anyone has library access to the study quoted in Nyttend's link, it is: "Heart and Mind in Conflict: The Interplay of Affect and Cognition in Consumer Decision Making'" (Baba Shiv, Alexander Fedorokhin, Journal of Consumer Research, University of Chicago Press, vol. 26(3), pages 278-92, December, 1999). link to JSTOR with abstract. I can't access the study directly, but this link suggests that 63% of the 7-digit memorizers chose chocolate cake, as opposed to only 41% of the 2-digit memorizers. ---Sluzzelin talk 16:40, 20 September 2010 (UTC)

Judging from the first page of the article and abstract, it doesn't seem like it is making an argument about brain energy at all, but a more complicated one about consumer choice. --Mr.98 (talk) 16:51, 20 September 2010 (UTC)

The first link posted said that there were 165 participants, so 63%=104, 41%=68, and ... maybe 7 people snarfed them both down while the proctor wasn't watching? It's hard to get excited enough to run a proper Poisson distribution on the data.

We should remember that for scientific publication, a 95% confidence in the statistics is the usual threshold, which means that one out of every 20 studies of bogus ideas will be accepted. In a field such as consumer choice, there may be quite a few such studies...

Also, they have no proof of the mechanism by which this might work. Bear in mind that a difficult mental task requires brainpower, which if I recall correctly runs on a pure and constant stream of glucose, more so than other organs. So it is possible that rather than being some kind of wise choice, this rather represents a short-term dip in blood glucose level. (I don't know this to be fact though) The obvious refinement that should have been done was to use an ordinary over the counter blood glucose meter to see whether the memorization had any effect on that, and whether that is correlated with the food choice. Wnt (talk) 19:10, 20 September 2010 (UTC)

Under the assumption that the groups are equal-sized (or as close as you can get), I ran the contingency table through Fisher's exact test and got a p value of 0.0077, so the data are actually pretty strong as these things go. Looie496 (talk) 21:32, 20 September 2010 (UTC)

Haven't looked at the actual paper itself (only OP's link summarizing it) -- how did they make sure they didn't cue the subjects when presenting the food choice? Anything else that looks like a design flaw to account for such robust statistics for what you'd think would be very weak results even if only because the difference in tasks was between "very very easy" and just "very easy"...? WikiDao ☯ (talk) 22:12, 20 September 2010 (UTC)

The study does not conclude conclusively that memorizing numbers "takes up" any more thinking capacity or brain resources than memorizing fewer numbers, even after the task is complete and it's time to pick dessert. Where would this extra "used" capacity go after the brain is no longer actively pursuing this task? Other than the students feeling they deserve tastier dessert, which I agree with, some other plausible explanations are that the students want more "energy" from all the sugar that the chocolate cake provides, that the extra use of brain resources were used in a promissory preparation for tastier dessert, or that there is no correlation at all between using more brain capacity and making healthy or self-disciplinary food choices. ~AH1^(TCU) 00:54, 21 September 2010 (UTC)